1. Field of the Invention
The present invention relates to a photo-conductive liquid crystal light valve for use in a projection type liquid crystal display device.
2. Background
The photo-conductive liquid crystal light valve is arranged such that a pair of transparent electrodes are disposed on the outside of a lamination structure of a photo-conductive layer, a liquid crystal layer laminated with a light reflection layer is interposed therebetween, and an AC voltage is applied between the pair of transparent electrodes. In this arrangement, when the element is irradiated with light from its writing side, the resistance of a portion of the photo-conductive layer irradiated with the light is reduced so that a voltage is applied to a portion of the liquid crystal layer corresponding to that portion of the photo-conductive layer and an image is written into the element.
As means for writing an image into such a photo-conductive liquid crystal light valve, known is, for example, an optical fiber tube constituted by a CRT (cathode-ray tube) and optical fibers connected to the CRT for leading an image displayed on the CRT to the photo-conductive liquid crystal light valve. FIG. 1 shows an example of the conventional projection type liquid crystal display device using such an optical fiber tube of the type as described above. As shown in FIG. 1, an image displayed on a CRT of an optical fiber tube 2 is written into a photo-conductive layer of a liquid crystal light valve 1 through optical fibers. Light emitted from a light source 3 enters into a polarizing beam splitter 6 through a mirror 4 and a condenser lens 5. P-polarization components of the incident light are passed through the polarizing beam splitter 6 as they are, and, to the contrary. S-polarization components of the light are perpendicularly deflected by the polarizing beam splitter 6 so as to enter the liquid crystal light valve 1.
In this case, if an image is being drawn in a liquid crystal layer of the liquid crystal light valve 1, the light reflected from the liquid crystal light valve 1 locally contains P-polarization components in accordance with the concentration of the image of the liquid crystal layer. Then, only the P-polarization components in the reflected light are passed through the polarizing beam splitter 6 as they are, so that an image corresponding to the P-polarization components is projected onto a screen 8 through a projection lens 7.
Thus, as means for writing an image into the photo-conductive liquid crystal light valve 1, the optical fiber tube 2 has been conventionally used. In the case of using the optical fiber tube 2, however, there has been a disadvantage in that the volume of space occupied by the optical fiber tube 2 is large because the CRT is large in depth and therefore the optical fiber tube 2 is disadvantageous with respect to size.
Further, as means for writing an image into the photo-conductive liquid crystal light valve 1, there is a two-dimensional scanner using laser light. In this case, there is a disadvantage in that a large amount of space is required and the structure is complicated and expensive.